Retinal oxygen consumption during hyperglycemia in patients with diabetes without retinopathy

Objective: This study aimed to determine whether retinal oxygen consumption in patients with diabetes without retinopathy is affected by acute changes in blood glucose. Design: The study design was a nonrandomized, interventional clinical study. Participants: The study consisted of 12 patients with diabetes without ophthalmoscopically visible diabetic retinopathy whose ages were 20 to 59 years (mean, 33.7 years). Intervention: Retinal vessel oximetry was performed on subjects during normoglycemia and during acutely induced hyperglycemia. Hyperglycemia was achieved with the ingestion of an oral glucose load, Main Outcome Measures: Changes in retinal arterial and venous blood oxygen saturation resulting from systemic blood glucose changes were measured. Measurements were made using a noninvasive, two-wavelength digital imaging retinal vessel oximeter. Results: In each subject, the measured retinal venous blood oxygen saturation decreased significantly during hyperglycemia. The amount of decrease in venous oxygen saturation associated with hyperglycemia was positively correlated with the duration of diabetes. The measured retinal arterial oxygen saturation did not change significantly during hyperglycemia, Conclusions: These results, taken with the observations of numerous other investigators that show increased blood flow during acute hyperglycemia, provide evidence of substantially increased retinal oxygen consumption during hyperglycemia. The results also complement previous observations of the effect of diabetes on retinal autoregulation.